41. A narrow beam of electrons with a speed of 20,000 km / s passes in a vacuum in the middle between the plates of a flat capacitor. What is the smallest potential difference you need to apply to the plates so that the electrons do not come out of the capacitor? The distance between the plates is 1 cm, their length is 3 cm.

Detailed solution. Decorated in Microsoft Word 2003. (Target decided to use formula editor)